This invention relates to an experimental nuclear fusion reactor, and more particularly to an experimental nuclear fusion reactor which generates an annular plasma with a coaxial plasma gun.
FIG. 1 shows an experimental nuclear fusion reactor in a prior art. Numeral 1 designates a metallic container which has a drum-shaped outer periphery, and in which a cylindrical center conductor 2 is centrally arranged. A plasma inlet 3 is constructed of a metallic tube in order to introduce an annular plasma into the container 1, a coaxial plasma gun (also called "Marshall gun") 4 serves to generate the annular plasma, and the annular plasma 5 is confined in the container 1. Numeral 6 indicates a vacuum vessel. Numerals 7 and 8 indicate the outer electrode and inner electrode of the coaxial plasma gun, respectively, which are arranged concentrically with each other.
Owing to the above construction, the coaxial plasma gun 4 executes an electric discharge to produce the annular plasma, and the produced plasma is introduced into the confinement container 1 through the inlet 3 and is settled in the state of the annular plasma 5 as shown in the figure. The annular plasma 5 thus settled in the container 1 has a poloidal magnetic flux interlinking with the plasma and a toroidal magnetic flux concentric with the plasma. When let stand, both the magnetic fluxes diffuse spatially. Consequently, the plasma diffuses and cannot be kept confined. Since, however, the container 1 is made of metal, an induced current flows in the toroidal direction of the container 1 and impedes the diffusion of the poloidal magnetic flux, so that the plasma can be held and confined within the container 1.
In the prior-art experimental nuclear fusion reactor described above, there is no current path in the poloidal direction. This has led to the problem that the toroidal magnetic flux cannot be held and diffuses out of the container, the diffusion affects the confinement of the plasma, and the confinement performance is not enhanced.